Trivia: Originally Clair and Chris Redfield were to appear in the film after having been featured in previous movies. But script-changes lead to them being written out, and their fates were left ambiguous. Clair will be re-appearing in the sixth film, however.
Trivia: The footage of the T-cells Wesker injects Alice with is reused from Resident Evil: Afterlife, only in that one, it's the cure for the virus.
Chosen answer: Jill was unconscious at the time, while Claire was awake, therefore the loss of memory may differ by state of mind, or vary from person to person.